1. Field of the Invention
The invention generally relates to land vehicles and their suspension means, especially to fluid suspensions. A method and its resultant product apparatus are disclosed, wherein a rubber suspension is converted to a fluid suspension that employs substantially the same physical housing structure as the original rubber suspension.
2. Description of the Prior Art
Off-highway suspension systems are employed on large-scale vehicles such as trucks, scrapers, dozers, loaders, tow tractors, and pushers. This type of equipment is used, for example, in construction, mining, and quarry work. One of the suspension systems in such use, produced by Unit Rig & Equipment Co. of Tulsa, Oklahoma, provides a suspension tube that is filled with stacked rubber impact pads, which provide ride damping. Another type of suspension system is the gas or hydro-strut, which employs an oil-filled suspension tube with nitrogen gas over the oil.
The rubber-damped type of strut is considered by many equipment operators to be too harsh. When used with off highway mining haul trucks, the rubber-damped strut, the ride is hard when the truck is loaded, and there is very little travel or ability to absorb shocks. The condition is similar or worse when the truck is empty, and due to excessive vibration, the life of many components is shortened. Vehicle frames have developed problems, and drivers often complain about the vibrations. However, once a vehicle is equipped with such a strut, the high cost of such a large strut prohibits change-over to the hydro-strut, as a single strut may have a cost on the order of twenty thousand dollars. Accordingly, there is a strong incentive to convert the rubber-damped type of strut into a hydro-strut, as this conversion can offer the damping characteristics of the latter without requiring a complete change of suspension components. A conversion of the type suggested herein can be achieved for a fraction of the price of a new strut and thereby offers an economic justification as well as a performance justifiction.
The end product is similar to a variety of known struts or shock absorbers that employ an oil and gas combination to achieve damping. For example, U.S. Pat. No. 2,914,337 to Kress discloses a suspension structure in which oil and gas filled chambers provide the required damping. U.S. Pat. No. 3,387,856 to Guilhamat et al discloses a hydro-pneumatic suspension system in which a compressed gas and a lubricating fluid operate in separate chambers. Hydro-pneumatic shock absorbers are disclosed in U.S. Pat. Nos. 2,440,353 to Wallace and 3,348,703 to Powell et al. A hydro-pneumatic suspension system especially adapted to high capacity vehicles is shown in U.S. Pat. No. 3,820,818 to Kress et al.
While conversion of rubber to oil damped suspension is believed new, some art is known in the area of altering and renewing sealed struts. For example, U.S. Pat. No. 4,261,446 to Bolger teaches a conversion of a sealed strut to one able to receive a shock absorber cartridge insert. Also of interest is U.S. Pat. No. Re. 31,212, which teaches a strut assembly designed to receive replacement shock absorbers. The referenced art shows the desirability of renewing the capability of struts. At the same time, the art demonstrates that renewal has consisted of rebuilding a strut according to its original structure or replacing a cartridge assembly. Conversion of between different inner damping media has not been suggested but offers a new capability.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, the strut and method of manufacture of this invention may comprise the following.